EWWW Image Optimizer plugin for WordPress is vulnerable to cross-site scripting, caused by improper validation of user-supplied input by the wp-admin/options-general.php script. A remote attacker could exploit this vulnerability using the page HTTP GET parameter in a specially-crafted URL to execute script in a victim's Web browser within the security context of the hosting Web site, once the URL is clicked. An attacker could use this vulnerability to steal the victim's cookie-based authentication credentials.